With your swamp situation...I would just estimate the major majority of the pond, but I invite others opinions on the matter.
Without seeing the pond or, at least, a good sketch of the pond (and swamp) with depths indicated...it's hard to detemine how much I would include of the swampy areas in the gallon estimate. 4.3 acres of swamp around a 0.7 acre pond could shift the calcualtions greatly depending on swamp depths and how readily availible the swamp waters are to the churning of the aeration system.
As for muck reductions from aeration...I'll leave that discussion to those more in the know. My pond was refurbished and one of the benefits of adding aeration was considered to be a tool to fight muck build-up, not necessarily to reduce it (I had none to reduce).
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